The invention relates to a screw nut comprising a metallic material with a threaded bore and an inner groove which is associated with the longitudinal axis of said threaded bore in radially circumferential fashion. In addition, the invention deals with a method for producing the screw nut and a tool developed therefor.
A nut and a method of the type mentioned at the outset are described in FR 2 557 652.
U.S. Pat. No. 2,363,680 describes a nut of another type, in which an annular collar is upset and a thread is provided on the inwardly pointing side face thereof. The upset part of the annular collar has a wall thickness which is larger than a wall thickness of the bent connecting part and of the adjacent part which has not been upset.
U.S. Pat. No. 2,952,289 discloses a nut, in which an annular collar is bent back and then axially compressed until it is positioned as close as possible to the free end of the nut.
U.S. Pat. No. 2,385,390 discloses a nut with an annular collar, which has cutouts.
A nut of another type is disclosed in the German patent 3 05 761, wherein the nut is provided with an annular hollow so as to form a safety nut, this process taking place by means of a drilling device on a machine tool with a revolving spindle, the spindle being aligned with a chuck for holding singular nuts or a plurality of nuts during the hollowing-out process. The hollow is formed before the thread is cut in. The hollow is located at the same distance from the two end faces of the nut. The thread is cut on both sides of the hollow with the same pitch. Then the nut is subjected to compression in order to achieve an offset of the thread parts on both sides of the hollow with respect to one another.
The Swiss patent 2 49 469 also demonstrates a safety nut which is provided at its unloaded end with a channel by means of part of the thread being removed, with the result that an annular tab is produced which is subjected to upset forging after the main part of the thread. This is another way of providing a securing screw nut.
The German patent 4 90 889 describes a securing action of a nut which is achieved by virtue of the fact that an annular groove with a wedge-shaped cross section is provided in the threaded bore, or in the core of the nut. In this case, too, the continuous thread is interrupted in the upper part of the nut by a cutout, which is designed in such a way that, as a result, a thin wall is produced, so that an upper subsection has a spring effect. Then, the upper subsection is constricted in terms of its diameter by being compressed and at the same time is compressed in terms of its height in order to achieve a cling effect of the nut. The thin wall piece which remains as a result of the cutout in this case produces a spring effect on the constricted and pitch-offset flank diameter of the upper thread part.
These and other known nuts have considerable disadvantages in terms of their operation, but in particular with a view to the complex manufacture which needs to take place in metal-cutting fashion by means of part of the thread or the walls of the nut being removed in order to achieve a sprung securing effect of a thread part.
In the knowledge of these particular facts, the inventor is confronted with the problem of providing a screw nut which can be used efficiently and primarily can be produced simply and quickly.